1. Field of the Invention
The present invention relates to a process and incinerator installation for thermally treating with a high-efficiency granular solid waste.
In the present specification and in the appended claims, the term "granular solid waste" is intended to include also granular solid waste having a high humidity content, such as granulated sludge.
2. Brief Description of the Prior Art
Burial of urban and industrial solid waste is less and less supportable on the economic and environmental points of view. Burial of solid waste and sludge is an expensive operation whose cost can be reduced through valorization of such waste before landfilling the unusable portion. Competitiveness and profitability of certain industries are closely related to the valorization, regeneration and efficient treatment of solid waste. Recent governmental regulations are more restrictive regarding the burial of solid waste without close control of the landfill leachate. Waste burial, when permitted, is more and more expensive due to control requirements (cellular burial, stabilization, etc.). Accordingly, it is urgent to consider any waste as a potential source of energy or even as a potential source of raw material.
The rigor of recent laws and regulations reflects the increasing concern of the population regarding the quality and protection of the environment. This is presently leading to the development of more versatile and performing technologies having a high destruction capability. The governmental policies initiated by the American Environment Protection Agency (EPA), are more and more oriented toward the promotion of the "best available technology". Such policies get around the problem of having to estimate the real level of risk for the environment and/or the health of the population associated to the operation of a given technology. In any case, this level of risk is very difficult to estimate.
These concerns and the continuously increasing volume of solid waste to be treated have resulted in the new challenge of developing processes capable of valorizing, regenerating and treating solid waste. Many approaches are available for treating solid waste: physical, thermal, biological and mechanical treatments. The approach to be used for a given application depends on many factors: the type of waste to be treated, the composition (fraction of organic matter, water, inert matter, etc.), the quantity, the size, the type of bond between the components of the waste, etc. The approach to be selected also strongly depends on the objectives of the treatment: elimination or degradation of an hazardous product, stabilization, recycling, energetic valorization, decontamination, volume reduction, etc.
An approach is selected in relation to its technical and economical performance. For example, energy recovery options are widely used in relation to solid waste having average or high organic contents. Energy recovery can be divided into three categories: incineration, gasification and pyrolysis. Selection of one or the other of these three categories depends on whether one wishes to conduct a direct valorization through heat recovery or an indirect valorization through production of combustible.
Incineration is recognized as the most interesting approach in several applications: the existing incineration technologies offer good technical, economical and environmental performance. Incineration can substantially reduce the volume of solid waste and a recovery of energy from the flue gas. In many situations, it can eliminate the contaminants and regenerate or valorize the solid waste being treated.
Application of the existing incineration technologies is limited since none of these technologies is capable of solving all the problems related to elimination and valorization of the solid waste; each case requiring its own solution. Moreover, many of the existing incineration technologies present the following drawbacks:
atmospheric pollution (displacement of the pollution); PA1 low capacity; PA1 low versatility; and PA1 high investment and operation costs. PA1 a) supplying granular solid waste to the bed; PA1 b) supplying granular solid waste and bed material from the lower portion of the chamber to the lower portion of the riser pipe directly in the flame; PA1 c) by means of the flame produced by the burner, burning the granular solid waste and heating the inside of the riser pipe; PA1 d) by means of the flue gas, pneumatically transporting the granular solid waste and bed material upwardly from the lower portion of the riser pipe to the upper end of that pipe so as to create turbulence in the riser pipe to thereby increase absorption of heat by the granular solid waste and oxidation of combustible components of the granular solid waste; PA1 e) discharging the granular solid waste and bed material in said chamber through the upper end of the riser pipe; and PA1 f) evacuating the flue gas from the incinerator installation. PA1 the reactor is a fast fluidized bed with inner circulation; PA1 the inside of the riser pipe is raised to a temperature .gtoreq.900.degree. C.; PA1 the granular solid waste and bed material is transported upwardly in the riser pipe at a speed between 3 and 15 meters/second; and PA1 the volume fraction of granular solid waste and bed material in the riser pipe is situated between 1% and 5% to further increase its velocity and the turbulence in the riser pipe.
In order to meet the new requirements related to the quality of treatment, several technologies have been developed or are presently being developed; these technologies operate at high temperature to convert large amounts of organic matter.